8th-Gen Intel Core (Kaby Lake-R) for Low-Power Laptops

This has been a big year for Intel low-power mobile chips. For generations we’ve put up with sub-10% year-on-year performance improvements, having Intel focusing on better efficiency and longer battery life. However, with AMD hot on Intel’s heels and set to launch their own ultraportable processors in the near future, Intel has decided that the time for incremental improvements is over.

With that, Intel’s low-power mobile chips have finally transitioned from a dual-core to quad-core design for the first time. This has been achieved while keeping within the same 15-watt TDP as previous low-power U-series chips, essentially allowing for a big jump in performance without a corresponding hit to battery life.

Before we discuss the specific changes to Intel’s new processors, let’s talk a bit about the basics, in particular Intel’s confusing product line for 2017.

These new quad-core mobile processors fall into Intel’s 8th generation lineup, which consists of products from three separate architectures: Coffee Lake, Cannon Lake, and Kaby Lake Refresh. This is in stark contrast to 7th gen products, which all used the Kaby Lake architectures.

There are a multitude of reasons why Intel has gone with a three architecture split for their 8th gen CPUs, but it basically comes down to Intel’s process nodes struggles, particularly in the transition to 10nm. It’s confusing for enthusiasts who like to dive into the architecture of Intel’s products, though most consumers will only need to see “8th generation” branding to know they’re getting the latest CPUs in their respective categories.

At the moment, the three architectures that form Intel’s 8th gen line are as follows:

Coffee Lake. These are Intel’s 8th generation CPUs for desktops, and potentially high-performance laptops in the future, built on a second refinement of Intel’s 14nm process (known as 14nm++).

Cannon Lake. These 8th gen processors are due for release in 2018, and consist of a 10nm die shrink of the Coffee Lake architecture. It’s not clear what parts will be included in the Cannon Lake line, though it’s expected to be low-power mobile parts.

Kaby Lake Refresh. These are Intel’s 8th generation CPUs for low-power laptops, built using the same 14nm+ process node and largely the same architecture as Kaby Lake.

If you’re interested in Coffee Lake chips for the desktop, you can read our review here, but for now we’ll be discussing Kaby Lake Refresh, or Kaby Lake-R, for ultraportable laptops.

As we mentioned earlier, the main improvement to Intel’s U-series 15W parts this year is the jump from two core, four thread processors with Kaby Lake, to four core, eight thread processors with Kaby Lake Refresh. The doubling of cores and threads is the only major change here, as Kaby Lake-R processors use the same microarchitecture (aside from minor tweaks) and the same 14nm+ manufacturing node as last year’s 7th gen mobile parts.

Intel’s low-power mobile chips have finally transitioned from a dual-core to quad-core design for the first time

The trade-off for more cores and threads in the same 15W TDP is base frequency, which is universally lower. On the other hand, Turbo frequencies are higher, even four-core Turbo speeds, while there’s also a handy increase to L3 cache: 8MB for Core i7 parts, and 6MB for Core i5 parts. All Kaby Lake-R parts support LPDDR3 and DDR4 memory, with DDR4 support increasing from DDR4-2133 to DDR4-2400.

Spec

Core i7-8550U

Core i7-7500U

Core i7-6500U

Core i7-5500U

Cores/Threads

4/8

2/4

Base Clock

1.8 GHz

2.7 GHz

2.5 GHz

2.4 GHz

1C Turbo Clock

4.0 GHz

3.5 GHz

3.1 GHz

3.0 GHz

2CTurbo Clock

4.0 GHz

3.5 GHz

3.0 GHz

2.9 GHz

4C Turbo Clock

3.7 GHz

N/A

GPU

UHD 620

HD 620

HD 520

HD 5500

Max. GPU Clock

1150 MHz

1050 MHz

1000 MHz

L3 Cache

8MB

4MB

TDP

15W

Unit Price

$409

$393

On the graphics front, the four Kaby Lake-R processors in this initial 8th gen release use Intel’s UHD 620 CPU, which is identical to the HD 620 used before. In other words, we’re still seeing 24 execution units with clock speeds of 1100 and 1150 MHz for Core i7 and i5 CPUs, respectively.

All things considered, the Core ix-8x50U line is a direct upgrade on the Core ix-7x00U series from last year. We’ll have to wait a bit longer for Intel to release their usual array of 15W and 28W U-series CPUs with more powerful Iris graphics, as well as ultra-low-power Y-series parts.

Of particular interest in this review is the Core i7-8550U, which is the direct successor to last year’s Core i7-7500U. The i7-8550U is the second-from-top Kaby Lake-R processor, with the flagship (for now) i7-8650U taking the performance crown with slightly higher clocks.

As with all Kaby Lake-R processors, the main gain here is the jump from a 2C/4T design to 4C/8T. Base clock speeds have reduced from 2.7 to 1.8 GHz, allowing the addition of an extra two cores into the same 15W TDP. However, boost frequencies have increased from 3.5 to 4.0 GHz for single and dual-core usage, and 3.7 GHz for all-core usage, provided there is enough power and thermal headroom. L3 cache is also up from 4MB to 8MB.

On the GPU side, under the new name of UHD 620, the i7-8550U’s GPU is almost the same as before but clocked up to 1150 MHz, which is a 100 MHz clock speed gain, across the same 24 execution units.

While you can’t go out and by a U-series chip off the shelf, it’s interesting to note that prices have increased slightly over last year’s lineup. The i7-8550U is now $409, up $16 from $393. This should have no material effect on laptop pricing, but it’s no real surprise that a larger CPU with more cores costs slightly more.

This performance review of the Core i7-8550U was conducted on a Dell Inspiron 13 7000 2-in-1, which provides a decent baseline platform for testing with its 16GB of DDR4-2400 RAM, high-performance 512GB M.2 SSD, and 1080p display. The results you’ll see in the coming pages should give you a good idea of how the i7-8550U will perform in a range of devices, not just the laptop we tested with.

Looking over the last 12 months of laptop testing we did with Kaby Lake, laptops that use the same CPU can vary by up to five percent in performance benchmarks...

Although, it’s important to note that exact performance figures will vary by small amounts from device to device, as different laptops use different thermal solutions and have different power targets. Looking over the last 12 months of laptop testing we did with Kaby Lake, laptops that use the same CPU can vary by up to five percent in performance benchmarks, so keep that in mind as we dive into how the Core i7-8550U performs.